I’m interpreting Demand Control Ventilation (DCV) as variation of fresh air quantity from 0% to 100% based on minimum ventilation code, exhaust air replacement, occupied space CO2 control or free cooling based on warmest zone requirements. ASHRAE may have a different definition. On October 5, 2020 ASHRAE posted a new sheet regarding “GUIDANCE FOR RE-OPENING BUILDINGS” with some significant changes from the previous HVAC re-opening advice of July 17, 2020 and August 20, 2020. We have two very dangerous social challenges simultaneously occurring globally: 1) The COVID-19 virus threat. The HVAC actions suggested via the major Engineering societies in Europe (REHVA) and North America (ASHRAE) will produce added Green House Gas emissions. 2) Climate change. Action required is to reduce Green house Gas emissions. We should not needlessly feed one of these monsters while attempting to address the other. Current scientific studies show that the virus cannot travel from infected persons in the occupied space to the remote HVAC fan system and back to the supply air diffusers in the occupied space. Scientific studies are required to quantify the virus content at HVAC locations identified at the locations A, B, C, D, E and F on page 11-203 of this report. Social distancing rules imply the virus cannot travel more than two metres to infect another person. The net result of these facts is the supply air entering the occupied space cannot contain virus whether it contains fully fresh air or fully recirculated air. With no added virus protection benefit, the system altered to full fresh air may require over 700% more heat (page 11-202) to keep the occupied space warm. This will produce 700% more GHG emissions, which will tend to escalate Climate Change. Often statements for better ventilation are voiced. The ventilation air from the supply fans must be considered from two different positions: 1) The air from the fan to the entrance point of the occupied space. 2) The air as it passes through the occupied space. If the issue is with virus being passed from an infected person to another within the occupied space, the problem will still exist even if the supply air to that space is completely virus-free fresh air. Current scientific studies and the virus travel distance defined by social distancing indicate that the supply air to the space must be virus-free. Altering fresh air rate and filters at the HVAC fan is pointless when the supply air is virus-free before and after the HVAC alterations. If the problem is only in the occupied space, it must be solved in the occupied space. We should avoid the addition of pointless GHG emissions to the atmosphere. The shift in operational changes via ASHRAE in the new positions posted October 5, 2020 must be conveyed very clearly to officials in school boards, government and teacher unions on ASHRAE’s altered 11.197
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